% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Airapetian:170112,
      author       = {Airapetian, Avetik and Akopov, N. and Akopov, Z. and
                      Augustyniak, W. and Avetissian, A. and Blok, H. P. and
                      Borissov, A. and Bryzgalov, V. and Capiluppi, M. and
                      Capitani, G. P. and Cisbani, E. and Ciullo, G. and
                      Contalbrigo, M. and Dalpiaz, P. F. and Deconinck, W. and De
                      Leo, R. and De Sanctis, E. and Diefenthaler, M. and Di
                      Nezza, P. and Düren, M. and Ehrenfried, M. and Elbakian, G.
                      and Ellinghaus, F. and Etzelmüller, E. and Fabbri, R. and
                      Felawka, L. and Frullani, S. and Gabbert, D. and Gapienko,
                      G. and Gapienko, V. and Garibaldi, F. and Gavrilov, G. and
                      Gharibyan, V. and Hartig, M. and Hasch, D. and Holler, Y.
                      and Hristova, I. and Ivanilov, A. and Jackson, H. E. and
                      Joosten, S. and Kaiser, R. and Karyan, G. and Keri, T. and
                      Kinney, E. and Kisselev, A. and Korotkov, V. and Kozlov, V.
                      and Kravchenko, P. and Krivokhijine, V. G. and Lagamba, L.
                      and Lapikás, L. and Lehmann, I. and Lenisa, P. and
                      Lorenzon, W. and Ma, B. -Q. and Mahon, D. and Manaenkov, S.
                      I. and Mao, Y. and Marianski, B. and Marukyan, H. and
                      Movsisyan, A. and Murray, M. and Naryshkin, Y. and Nass, A.
                      and Nowak, W. -D. and Pappalardo, L. L. and Perez-Benito, R.
                      and Petrosyan, Anush and Reimer, P. E. and Reolon, A. R. and
                      Riedl, C. and Rith, K. and Rostomyan, A. and Ryckbosch, D.
                      and Schäfer, A. and Schnell, Gunar and Schüler, K. P. and
                      Seitz, B. and Shibata, T. -A. and Stahl, M. and Stancari, M.
                      and Statera, M. and Steffens, E. and Steijger, J. J. M. and
                      Taroian, S. and Terkulov, A. and Truty, R. and Trzcinski, A.
                      and Tytgat, M. and Van Haarlem, Y. and Van Hulse, C. and
                      Vikhrov, V. and Vilardi, I. and Wang, S. and Yaschenko, S.
                      and Yen, S. and Zeiler, D. and Zihlmann, B. and Zupranski,
                      P.},
      collaboration = {{HERMES Collaboration}},
      title        = {{S}pin density matrix elements in exclusive $\omega$
                      electroproduction on $\mathrm{^1 {H}}$ and $\mathrm{^2 {H}}$
                      targets at 27.5 {G}e{V} beam energy},
      address      = {Berlin},
      publisher    = {Springer},
      reportid     = {DESY-2014-03012, DESY-14-116. arXiv:1407.2119},
      year         = {2014},
      abstract     = {Exclusive electroproduction of $\omega $ mesons on
                      unpolarized hydrogen and deuterium targets is studied in the
                      kinematic region of $Q^2> 1.0$  GeV$^2$ , 3.0 GeV  $< W
                      <$  6.3 GeV, and $-t'< 0.2$  GeV$^2$ . Results on the
                      angular distribution of the $\omega $ meson, including its
                      decay products, are presented. The data were accumulated
                      with the HERMES forward spectrometer during the 1996–2007
                      running period using the 27.6 GeV longitudinally polarized
                      electron or positron beam of HERA. The determination of the
                      virtual-photon longitudinal-to-transverse cross-section
                      ratio reveals that a considerable part of the cross section
                      arises from transversely polarized photons. Spin density
                      matrix elements are presented in projections of $Q^2$ or
                      $-t'$ . Violation of $s$ -channel helicity conservation is
                      observed for some of these elements. A sizable contribution
                      from unnatural-parity-exchange amplitudes is found and the
                      phase shift between those amplitudes that describe
                      transverse $\omega $ production by longitudinal and
                      transverse virtual photons, $\gamma ^{*L} \rightarrow \omega
                      _{T}$ and $\gamma ^{*T} \rightarrow \omega _{T}$ , is
                      determined for the first time. A hierarchy of helicity
                      amplitudes is established, which mainly means that the
                      unnatural-parity-exchange amplitude describing the $\gamma
                      ^*_T \rightarrow \omega _T$ transition dominates over the
                      two natural-parity-exchange amplitudes describing the
                      $\gamma ^*_L \rightarrow \omega _L$ and $\gamma ^*_T
                      \rightarrow \omega _T$ transitions, with the latter two
                      being of similar magnitude. Good agreement is found between
                      the HERMES proton data and results of a pQCD-inspired
                      phenomenological model that includes pion-pole
                      contributions, which are of unnatural parity.},
      keywords     = {positron p: exclusive reaction (INSPIRE) / electron p:
                      exclusive reaction (INSPIRE) / electron deuteron: exclusive
                      reaction (INSPIRE) / polarized beam: longitudinal (INSPIRE)
                      / omega(783): electroproduction (INSPIRE) / angular
                      distribution (INSPIRE) / cross section: longitudinal
                      (INSPIRE) / cross section: transverse (INSPIRE) / cross
                      section: ratio (INSPIRE) / spin: density matrix (INSPIRE) /
                      helicity: amplitude analysis (INSPIRE) / quantum
                      chromodynamics: perturbation theory (INSPIRE) / pi: pole
                      (INSPIRE) / HERMES (INSPIRE) / experimental results
                      (INSPIRE) / DESY HERA Stor (INSPIRE) / 27.6 GeV (INSPIRE)},
      cin          = {HERMES},
      ddc          = {530},
      cid          = {I:(DE-H253)HERMES-20120731},
      pnm          = {Experiments at HERA (HERMES) (POF2-511)},
      pid          = {G:(DE-H253)POF2-HERA-Exp.-(HERMES)-20130405},
      experiment   = {EXP:(DE-588)4517776-4},
      typ          = {PUB:(DE-HGF)25 / PUB:(DE-HGF)29},
      eprint       = {1407.2119},
      howpublished = {arXiv:1407.2119},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:1407.2119;\%\%$},
      url          = {https://bib-pubdb1.desy.de/record/170112},
}